Dielectric filter

Abstract

A dielectric filter includes two dielectric resonators each having a dielectric base body including first, second, third and fourth side surfaces and first and second end surfaces. A through hole is provided from the first end surface to the second end surface to define an inner surface. An outer conductor is located on and partially covers the four side surfaces. Uncovered portions of the second and third side surfaces are provided that are adjacent to each other and bounded by the outer conductor in three directions. An uncovered portion of the fourth side surface is adjacent to an uncovered portion of the first side surface and the first end surface, and is separated from the third side surface by the outer conductor. An inner conductor is located on the inner surface. A connection conductor is also located on the second end surface and connects the inner conductor to the outer conductor. An interstage coupling electrode is located on the uncovered portion of the first side surface. An area of the uncovered portion of the first side surface extends in at least three directions from the interstage coupling electrode and separates the interstage coupling electrode from the outer conductor. An input/output coupling electrode is located on the uncovered portion of the second and third side surfaces. Areas of the uncovered portions of the second and third side surfaces extend in three directions from the input/output coupling electrode and separate the input/output coupling electrode from the outer conductor. The the outer conductor of a first dielectric resonator is electrically connected to the outer conductor of a second dielectric resonator.

What is claimed is: 
     
       1. A dielectric filter comprising: at least two dielectric resonators each including:   a respective dielectric base body including corresponding first, second, third and fourth side surfaces and first and second end surfaces, wherein a respective through hole is provided from the first end surface to the second end surface along a central axis of the corresponding dielectric base body to define a respective inner surface thereof;   a respective outer conductor located on and partially covering the first, second, third and fourth side surfaces of the corresponding dielectric base body, wherein the outer conductor provides an uncovered portion of the first side surface that extends across a width of the respective first side surface and is adjacent to the corresponding first end surface, uncovered portions of the respective second and third side surfaces that are adjacent to each other and bounded by the corresponding outer conductor in three directions, and uncovered portion of the respective fourth side surface that is adjacent to the uncovered portion of the corresponding first side surface and the corresponding first end surface and is separated from the corresponding third side surface by the respective outer conductor;   a respective inner conductor located on the inner surface of the corresponding dielectric base body;   a respective connection conductor located on the second end surface of the corresponding dielectric base body, wherein the respective connection conductor connects the inner conductor to the outer conductor on the corresponding dielectric base body;   a respective interstage coupling electrode located on the uncovered portion of the corresponding first side surface, wherein a respective area of the uncovered portion of the corresponding first side surface extends in at least three directions from the respective interstage coupling electrode and separates the interstage coupling electrode from the corresponding outer conductor; and   a respective input/output coupling electrode located on the uncovered portion of the second and third side surfaces of the corresponding dielectric base body, wherein respective areas of the uncovered portions of the corresponding second and third side surfaces extend in three directions from the input/output coupling electrode and separate the respective input/output coupling electrode from the corresponding outer conductor;   wherein the respective dielectric resonators are connected with each other in such a manner that the outer conductor of a first one of the dielectric resonators is electrically connected to the outer conductor of a second one of the dielectric resonators.   
     
     
       2. A dielectric filter as claimed in claim 1, wherein the interstage coupling electrode of the first one of the dielectric resonators is electrically connected to the interstage coupling electrode of the second one of the dielectric resonators. 
     
     
       3. A dielectric filter comprising: at least two dielectric resonators each including:   a respective dielectric base body including corresponding first, second, third and fourth side surfaces and first and second end surfaces, wherein a respective through hole is provided from the first end surface to the second end surface along a central axis of the corresponding dielectric base body to define a respective inner surface thereof;   a respective outer conductor located on the first, second, third and fourth side surfaces of the corresponding dielectric base body, wherein the respective outer conductor covers the fourth side surface and leaves an uncovered portion of the first side surface that is adjacent to the first end surface and bounded in three directions by the corresponding outer conductor, and uncovered portions of the respective second and third side surfaces that are adjacent to each other and bounded by the corresponding outer conductor in three directions;   a respective inner conductor located on the inner surface of the corresponding dielectric base body;   a respective connection conductor located on the second end surface of the corresponding dielectric base body, wherein the respective connection conductor connects the inner conductor to the outer conductor on the corresponding dielectric base body;   a respective interstage coupling electrode located on the uncovered portion of the corresponding first side surface, wherein a respective area of the uncovered portion of the corresponding first side surface extends in three directions from the respective interstage coupling electrode and separates the respective interstage coupling electrode from the corresponding outer conductor; and   a respective input/output coupling electrode located on the uncovered portion of the second and third side surfaces of the corresponding dielectric body, wherein a respective area of the uncovered portions of the corresponding second and third side surfaces extend in three directions from the respective input/output coupling electrode and separate the respective input/output coupling electrode from the corresponding outer conductor;   wherein the respective dielectric resonators are connected with each other in such a manner that the outer conductor of a first one of the dielectric resonators is electrically connected to the outer conductor of a second one of the dielectric resonators.   
     
     
       4. A dielectric filter as claimed in claim 3, wherein the interstage coupling electrode of the first one of the dielectric resonators is electrically connected to the interstage coupling electrode of the second one of the dielectric resonators.